[sdiy] Hammond 102100 pdf's finally up

[Aaron Lanterman]

On Mar 30, 2010, at 5:23 PM, Scott Nordlund wrote:

> Just took a look at this, have you ever seen a VCF like that before? 
> It's really unusual.  It looks like a highpass filter inside a feedback
> loop.


*thinks* 

Ah, I have seen such a thing before:

http://users.ece.gatech.edu/~lanterma/paten ts/hammond_fet_vcf.pdf

The Buchla 191 sharp cutoff filter is similar in spirit; its lowpass sections have highpass filters in loops of op amps (really op-amp-like things made with discrete transistors)

- Aaron